Simplified Torso Research Articles

Effect of torso reflections from simplified torso models on head-related transfer function simulation and ipsilateral perception of elevation

The effect of torso reflection on head-related transfer functions (HRTFs) is considered a suitable elevation localization cue for lateral sound sources below 3.0 kHz, and various torso models have been hitherto adopted in HRTF simulation. However, their torso reflection effects have not been compared in detail. This work analyzes the torso reflection effects of the representative torso models on HRTFs, and further evaluates their elevation localization performance via psychoacoustic experiments. The results show that the semi-ellipsoidal torso and truncated Knowles Electronics Mannequin for Acoustic Research (KEMAR) torso, both of which have considerable advantages over the spherical torso, can achieve better elevation localization performance, which validates the torso with human-like shape provide enough torso reflection and have a better ability in low-frequency lateral elevation perception.

Impact of the phantom geometry on the evaluation of the minimum detectable activity following a radionuclide intake: From physical to numerical phantoms

The establishment of an in vivo internal monitoring programme requires the use of phantoms to represent an activity distribution of an incorporated radionuclide within the body. The aim of this study was to quantify the impact of the phantom geometry on the minimum detectable activity (MDA) of an incorporated radionuclide. The MDA was assessed for two instruments: a conventional radiation protection instrument and a portable gamma spectrometer. Four phantoms were considered: two physical phantoms, a simplified torso phantom and a commercial whole body phantom, as well as two numerical phantoms, the reference adult male and female voxel phantoms published by the International Commission on Radiological Protection (ICRP). The phantoms were loaded with activity at the level of the thorax and abdomen using reference sources of 57Co, 133Ba, 137Cs, 60Co and 152Eu. The MDA for both instruments was experimentally assessed using the two physical phantoms. The experimental setup was modelled in GEANT4 and the simulated instrument responses were validated by the experimental data. The Monte Carlo model was then used to compute the instruments response and corresponding MDA when using the ICRP voxel phantoms. The simplified torso phantom provided one of the highest MDA estimates, up to a factor of 5 higher than the ones obtained with the voxel phantoms when considering a 57Co source. Depending on the considered source distribution within the phantoms, physical phantoms may lead to an underestimation of the MDA when compared to more complex and anatomically accurate numerical phantoms. This work presents a quantitative comparison between the MDA obtained with different phantoms and radionuclide distributions.

Noninvasive finding of local repolarization changes in the heart using dipole models and simplified torso geometry

Two inverse methods using dipole models for noninvasive assessment of local repolarization changes were investigated and compared in the simulation study. Lesions with changed repolarization were modeled by shortening of the action potential durations in ventricular regions typically influenced by occlusion of coronary arteries. Corresponding body surface potentials were computed using a multiple dipole model of the cardiac generator and an inhomogeneous torso model. Position of each lesion was then estimated by an inverse solution to a single dipole and to a group of five neighbouring dipoles. For both methods the lesion localization error was evaluated and its dependence on the lesion size and the noise in input data was studied. When no noise was present in the input data, the use of the inverse method to a group of dipoles instead of a single dipole resulted in an unsubstantial reduction of the mean localization error of small lesions from 0.6 to 0.5cm. For medium and especially for large lesions the mean localization errors decreased significantly from 1.1 to 0.6cm and from 2.3 to 1.0cm, respectively. The inverse solution to a group of five dipoles was more sensitive to noise. However, for large lesions it still gave better results than the solution to a single dipole if the signal to noise ratio was higher than 30dB.

Spatial-temporal filter effect in a computer model study of ventricular fibrillation / Räumlicher und zeitlicher Filtereffekt in einer Computermodellstudie zum Herzkammerflimmern

Prediction of countershock success from ventricular fibrillation (VF) ECG is a major challenge in critical care medicine. Recent findings indicate that stable, high frequency mother rotors are one possible mechanism maintaining VF. A computer model study was performed to investigate how epicardiac sources are reflected in the ECG. In the cardiac tissues of two computer models - a model with cubic geometry and a simplified torso model with a left ventricle - a mother rotor was induced by increasing the potassium rectifier current. On the epicardium, the dominant frequency (DF) map revealed a constant DF of 23 Hz (cubic model) and 24.4 Hz (torso model) in the region of the mother rotor, respectively. A sharp drop of frequency (3-18 Hz in the cubic model and 12.4-18 Hz in the torso model) occurred in the surrounding epicardial tissue of chaotic fibrillatory conduction. While no organized pattern was observable on the body surface of the cubic model, the mother rotor frequency can be identified in the anterior surface of the torso model because of the chosen position of the mother rotor in the ventricle (shortest distance to the body surface). Nevertheless, the DFs were damped on the body surfaces of both models (4.6-8.5 Hz in the cubic model and 14.4-16.4 Hz in the torso model). Thus, it was shown in this computer model study that wave propagation transforms the spatial low pass filtering of the thorax into a temporal low pass. In contrast to the resistive-capacitive low pass filter formed by the tissue, this spatial-temporal low pass filter becomes effective at low frequencies (tens of Hertz). This effect damps the high frequency components arising from the heart and it hampers a direct observation of rapid, organized sources of VF in the ECGs, when in an emergency case an artifact-free recording is not possible.

3D 동체 모형을 이용한 2D 전개 패턴 연구

To understand the basic relationship between 3D curved surface model and 2D pattern, simplified torso model was generated by commercial CAD program (IDEAS). 3D torso model was then divided into different blocks and unfolded into a flat pattern as in ordinary works of clothing item design. As results, 2D pattern development of different part of 3D torso model was attempted and analyzed mathematically. It was found that different height, radius and tangent slope of 3D blocks resulted in different 2D pattern. The relationships between the shape parameters of 3D torso blocks and those of 2D patterns were analyzed using regression equations. Direct way of drawing a 2D pattern of corresponding 3D torso block was also illustrated for the convenience of pattern making using conventional measurements of upper/ lower radii and height of 3D torso block.

Performance of personal inhalable aerosol samplers in very slowly moving air when facing the aerosol source.

While personal aerosol samplers have been characterized primarily based on wind tunnel tests conducted at relatively high wind speeds, modern indoor occupational environments are usually represented by very slow moving air. Recent surveys suggest that elevated levels of occupational exposure to inhalable airborne particles are typically observed when the worker, operating in the vicinity of the dust source, faces the source. Thus, the first objective of this study was to design and test a new, low cost experimental protocol for measuring the sampling efficiency of personal inhalable aerosol samplers in the vicinity of the aerosol source when the samplers operate in very slowly moving air. In this system, an aerosol generator, which is located in the centre of a room-sized non-ventilated chamber, continuously rotates and omnidirectionally disperses test particles of a specific size. The test and reference samplers are equally distributed around the source at the same distance from the centre and operate in parallel (in most of our experiments, the total number of simultaneously operating samplers was 15). Radial aerosol transport is driven by turbulent diffusion and some natural convection. For each specific particle size and the sampler, the aerosol mass concentration is measured by weighing the collection filter. The second objective was to utilize the new protocol to evaluate three widely used aerosol samplers: the IOM Personal Inhalable Sampler, the Button Personal Inhalable Aerosol Sampler and the 25 mm Millipore filter holder (closed-face C25 cassette). The sampling efficiencies of each instrument were measured with six particle fractions, ranging from 6.9 to 76.9 micro m in their mass median aerodynamic diameter. The Button Sampler efficiency data demonstrated a good agreement with the standard inhalable convention and especially with the low air movement inhalabilty curve. The 25 mm filter holder was found to considerably under-sample the particles larger than 10 micro m; its efficiency did not exceed 7% for particles of 40-100 micro m. The IOM Sampler facing the source was found to over-sample compared with the data obtained previously with a slowly rotating, freely suspended sampler in a low air movement environment. It was also found that the particle wall deposition in the IOM metallic cartridge was rather significant and particle size-dependent. For each sampler (IOM, Button and C25) the precision was characterized through the relative standard deviation (RSD) of the aerosol concentration obtained with identical samplers in a specific experiment. The average RSD was 14% for the IOM Sampler, 11% for the Button Sampler and 35% for the 25 mm filter cassette. A separate set of experiments, performed with the Simplified Torso showed that in very slowly moving air a personal sampler can be adequately evaluated even when it is not attached to a body but freely suspended (confirming the data reported previously).

MEASUREMENT OF THE SAMPLING EFFICIENCY OF PERSONAL INHALABLE AEROSOL SAMPLERS USING A SIMPLIFIED PROTOCOL

Traditional protocols for the performance evaluation of personal inhalable aerosol samplers utilize full-size manikins and large cross-section wind tunnels. Thus, these sampler evaluation procedures are complex, very costly, and time consuming. In addition, it is difficult to provide an adequately uniform wind velocity and aerosol concentration over large cross-section wind tunnels. A simplified test protocol, developed in our recent studies, is evaluated in this paper. The protocol is based on a three-dimensional rectangular simplified torso that simulates the dimensions of the human chest. This arrangement allows simultaneous measurement in four discrete orientations to the wind, thus providing useful orientation-dependent sampler information and possibly reducing the number of measurements needed. Sampling efficiencies of four personal inhalable aerosol samplers (the IOM, GSP, 37-mm closed-face cassette, and the button sampler) were measured using the simplified test protocol and the traditional approach for three particle sizes (7, 29, and 70 μm) in four inlet orientations to the wind (0, 90, 180, and 270°) and two wind velocities (0.5 and 2.0 m s -1). It was found that when these samplers were mounted on the simplified torso versus the full-size manikin, the sampling efficiencies responded to changes in the sampling conditions in the same way regardless of whether the samplers were mounted on the simplified torso or the full-size manikin. Also, the sampling efficiencies were found not to be statistically different when the samplers were mounted on the simplified torso versus the full-size manikin. Thus, the simplified test protocol was shown to be suitable for the performance evaluation of personal inhalable aerosol samplers.

Performance evaluation of personal aerosol samplers using full-size manikin and simplified torso

Performance evaluation of personal aerosol samplers using full-size manikin and simplified torso

Simplified method for testing personal inhalable aerosol samplers

The presently available protocol for evaluating the performance of personal aerosol samplers according to the inhalable convention is difficult to satisfy as it requires a large cross-section wind tunnel. The present study was initiated to simplify and reduce the cost of the test method by mounting the test samplers on a small, stationary torso instead of a full-size rotating manikin. The simplified torso consisted of a rectangular three-dimensional body (33 cm wide, 21 cm deep, 21 cm high). Replicates of the personal inhalable aerosol sampler under consideration were attached in the center of each vertical face of the simplified torso representing the three principal sampling orientations (facing the wind, turned 90°, and turned 180° to the wind). When the samplers were mounted on a full-size manikin, the air flow in the vicinity of the manikin was found to depend on the sampler location, symmetry of the manikin, and position of the manikin’s arms. On the simplified torso, the magnitude and direction of the air flow near the samplers were found to be comparable to that of the manikin. When subjected to nearly monodisperse aerosol flows (particle size of 70 μm, wind velocity of 50 and 200 cm s -1), both methods yielded aerosol sampling efficiencies that were statistically not different at three major sampling orientations. The advantages of the simplified torso are that fewer measurements need to be made; a smaller, less expensive wind tunnel can be used for the testing; and interlaboratory variability of personal inhalable samplers’ performance may be decreased.

Optimisation of the locations of multiple-dipole heart generators in a simple torso model

Electrocardiographic inverse solutions frequently assume multiple-dipole equivalent generators with locations fixed throught the QRS complex. This paper describes investigations which extend the solution to optimise the dipole locations at any instant of time. The combined results lead to a moving multiple-dipole inverse solution which is more accurate than the conventional solutions at each instant and also contains information related to the dynamic movement of the physiological generators. Tests so far have been limited to a 3-dipole solution in a highly simplified torso model. The generators in this study were dipoles displaced varying amounts from a standard central location; the inverse solution starts by using the standard location and then is led to an improved solution by a guided search. Moderate displacements, as compared to the size of the heart model, were shown to yield root mean square errors in the inverse-solution source strengths as high as 40% when the latter were found via a least-mean-square procedure. The method of steepest descent was utilised in the second step to improve the locations and strengths of the initially assumed equivalent-dipole generators and thus improve the accuracy of the inverse solution. The percentage root-mean-square source-strength errors were reduced from as high as 40% to under 10% in most cases. The initial position error of up to 10% for the source dipoles typically was reduced to less than 5% throught the use of the search routine. The ability of the solution dipoles to track the original locations was demonstrated.

Effect of torso geometry on the magnetocardiogram

Calculations of the effect of torso geometry on the extracorporeal magnetic field produced by a simple cardiac source have been carried out. Contrary to the results at present in the literature, it is found that the field solution is stable under perturbations of geometry in the sense that small relative changes in geometry produce comparably small changes in the magnetic field. Thus, simplified torso models may have a wider range of validity and usefulness than was previously thought.